On April 15, 1861, one day after the surrender of Fort Sumter propelled the nation into civil war, President Abraham Lincoln issued a proclamation calling for 75,000 state militiamen to suppress the Southern rebellion. Thousands of loyal men throughout the Midwest were quick to respond. The rapid buildup of local regiments required the United States War Department to create structure out of chaos. On May 3, 1861, Washington officials issued General Orders, No. 14, which created a new military unit known as the Department of the Ohio, merging regiments from the states of Ohio, Indiana, and Illinois. Major General George B. McClellan commanded the new department from his headquarters at Cincinnati, Ohio. McClellan oversaw the department until the War Department assigned him command of the Division of Washington under General Orders, No. 47, dated July 25, 1861. Following McClellan’s departure, Brigadier-General Ormsby M. Mitchel commanded the Department of the Ohio from September 19 to November 15, 1861.
Department of Kentucky
Meanwhile, south of the Ohio River, Kentucky officials were attempting to avoid involvement in the insurrection. One day after Lincoln issued his call for volunteers, Kentucky Governor Beriah Magoffin tersely responded that Kentucky would provide no troops. On May 24, the Kentucky legislature passed a resolution officially declaring the state’s neutrality.
Despite Kentucky’s efforts to remain neutral, recruiters on both sides sought volunteers throughout the state. By May 28, 1861, enough pro-Union regiments existed to prompt the U.S. War Department to organize the Department of Kentucky, which included as much of the state of Kentucky that lay within one hundred miles of the Ohio River. Brigadier General Robert Anderson, who had recently surrendered Fort Sumter, commanded the new department.
Department of the Cumberland
On August 15, 1861, the War Department issued General Orders, No. 57, which replaced the Department of Kentucky with an expanded department that included all of Kentucky and Tennessee. Officials named the new subdivision the Department of Cumberland.
During Anderson’s tenure, troops commanded by Confederate General Leonidas Polk invaded Columbus, Kentucky, ending all illusions that the state would escape the War Between the States. Within one week, voters in Kentucky elected a new Unionist legislature that voted to end the state’s neutrality.
Department of the Ohio
On October 7, 1861, the War Department issued General Orders, No. 6, directing Major General William T. Sherman to relieve Anderson, who had taken ill. The next day, Sherman issued General Orders, No. 7, assuming command of the department. One month later, when Sherman began to act erratically due to stress, he asked his superiors to relieve him of his command.
On November 9, 1861, the War Department issued General Orders, No. 97, which dissolved the Department of the Cumberland and expanded the Department of the Ohio to include the states of Ohio, Indiana, Michigan, Tennessee, and Kentucky east of the Cumberland River. Officials selected Brigadier General Don Carlos Buell to command the department, with headquarters at Louisville, Kentucky. When Buell assumed command on November 15, 1861, he found the structure, discipline, and training of troops under his command to be lacking and immediately set about remedying the situation. By December, Buell had organized the forces under his command into five divisions that became known as the Army of the Ohio.
Battle of Mill Springs
On January 19, 1862, the Army of the Ohio defeated Confederate troops commanded by Major-General George B. Crittenden at the Battle of Mill Springs, Kentucky. The Union victory forced the Rebels to abandon eastern Kentucky and to retreat into Tennessee.
Occupation of Nashville
Buell’s army then moved southeast toward Nashville. On February 25, 1862, the Army of the Ohio marched into the Tennessee capital unopposed, making Nashville the first Confederate state capital to fall into Union hands during the Civil War.
Department of the Mississippi
Shortly after the occupation of Nashville, President Lincoln issued War Order Number 3, which merged three western departments, including the Department of the Ohio into the Department of the Mississippi, commanded by Major-General Henry Halleck. The Army of the Ohio, still under Buell’s command, comprised 94,783 men, with 73,472 of these soldiers combat-ready.
Battle of Shiloh
While Lincoln was reorganizing his armies in the West, Confederate General Joseph E. Johnston was gathering his forces at Corinth, Mississippi, where the Western and Charleston Railroad and the Ohio and Mobile Railroad intersected.
To prepare for a general move against Corinth, Halleck ordered Buell to move the Army of Ohio to Savannah, Tennessee, located on the eastern bank of the Tennessee River, approximately thirty-five miles north of Corinth. From there, the Army of the Ohio moved nearly ten miles downstream, on April 6, 1861, to support Major-General Ulysses S. Grant and his Army of the Tennessee on the first day of the Battle of Shiloh. Buell’s arrival near sunset boosted the morale of Grant’s weary troops and enabled Grant to take the offensive and to win the battle on the next day.
Siege of Corinth
Following the Battle of Shiloh, Halleck arrived at Pittsburg Landing on April 11 and assumed field command of all of his forces. Halleck organized his troops into left, center, and right wings. Buell’s Army of the Ohio comprised the center wing. Halleck then advanced cautiously toward Corinth over the next two weeks. Following a short siege, he occupied Corinth, after the Rebel forces, commanded by General P. G. T. Beauregard, escaped unscathed.
In the wake of the loss of Corinth, Confederate President Jefferson Davis relieved Beauregard of command of the Army of Mississippi on June 27, 1862, and replaced him with Braxton Bragg. Following Bragg’s ascension, the focus of the war in Tennessee moved east to Chattanooga. Halleck ordered Buell to capture the important rail hub, but Bragg beat him there.
Confederate Heartland Campaign
As Buell approached Chattanooga, Bragg went on the offensive and launched an invasion of Kentucky, threatening Buell’s supply lines back to Louisville. Bragg left Chattanooga in August with nearly 34,000 men, with plans to unite with Lieutenant General Edmund Kirby Smith’s 18,000 soldiers, stationed near Knoxville, Tennessee, and then to move against the Army of the Ohio.
Initially, events went well for the Confederates. Smith left Knoxville on August 14, 1862, and he defeated a Union garrison at Richmond, Kentucky on August 30. Bragg’s army captured an important rail station, along with 4,000 Union soldiers, at the Battle of Munfordville (September 14–17, 1862). Throughout September, the two-headed Rebel onslaught forced Buell back towards Louisville. There, soldiers from across the Ohio River reinforced the Army of the Ohio.
In early October, with up to 60,000 men under his command, Buell left Louisville and became the pursuer. Smith and Bragg had still not combined their armies, and the Confederates were unprepared for Buell’s advance.
Battle of Perryville
On October 7, 1862, Buell’s army approached the small crossroads town of Perryville, Kentucky in three columns. There, the first column to arrive, commanded by Major General Alexander M. McCook, engaged 16,000 of Bragg’s men, commanded by Major General Leonidas Polk. Bragg rushed to Perryville and took command by 10:00 a.m. on October 8. Facing stubborn resistance, the Rebels gradually drove the Federals back. As the day progressed, however, more of Buell’s army arrived on the scene. Running short of supplies and ammunition and faced with the prospect of squaring off with the bulk of the Army of the Ohio on the following day, Bragg withdrew during the night.
After the Battle of Perryville, Bragg retreated to Harrodsburg, Kentucky, where he joined forces with Kirby Smith. The combined Confederate force was now comparable in size to the Army of the Ohio. Nevertheless, Bragg lost his enthusiasm for the campaign. Over the objections of Smith, Polk, and other subordinates, Bragg called off the Confederate Heartland Campaign and evacuated Kentucky, leaving the state in Union control for the rest of the war.
Buell’s half-hearted pursuit of Bragg as the Confederates withdrew from Kentucky, combined with his slow advance toward Chattanooga during the summer, triggered a great deal of criticism from Washington. Consequently, on October 24, 1862, the War Department issued General Orders, No. 168, which created the Department of the Cumberland, encompassing all of Tennessee east of the Tennessee River, plus any parts of northern Alabama and Georgia that Union troops might capture. The directive also placed Major General William S. Rosecrans in charge of all U.S. forces within the new department, including the Army of the Ohio. A dispatch from Halleck to Buell on the same day relieved Buell of his command.
General Orders, No. 168 also designated all of Rosecrans’ forces as the 14th Corps, thus ending the existence of the Army of the Ohio. The 14th Corps soon became known as the Army of the Cumberland, re-gaining its designation from the days of Anderson’s and Sherman’s command in 1861. The Army of the Cumberland served with valor during the Battle of Stones River (December 31, 1862–January 2, 1863), the Battle of Chickamauga (September 19–20, 1863), the Chattanooga Campaign (October–November 1863), the Atlanta Campaign (May 7–September 2, 1864), and the Franklin-Nashville Campaign (September 18–December 27, 1864).